Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$96.35	13.866%	$109.7099	$109.71	$109.70	$109.70
Purchase #2	$56.49	4.257%	$58.8948	$58.89	$58.90	$58.90
Purchase #3	$149.89	10.120%	$165.0589	$165.06	$165.05	$165.10
Purchase #4	$227.52	7.298%	$244.1244	$244.12	$244.10	$244.10
Purchase #5	$76.61	12.504%	$86.1893	$86.19	$86.20	$86.20
Purchase #6	$69.67	9.656%	$76.3973	$76.40	$76.40	$76.40
Purchase #7	$245.63	13.632%	$279.1143	$279.11	$279.10	$279.10
7 purchase totals =	$922.16		$1,019.4889	$1,019.48	$1,019.45	$1,019.50